Evaluation of Steel Slag Fine Aggregate in Hot-Mix Asphalt Mixtures

Abstract

Since a considerable amount of steel slag is produced in the southwestern part of Pennsylvania around Pittsburgh, where natural fine aggregate sources are limited, an evaluation was undertaken to determine the feasibility of using “cured” steel slag fine aggregate in hot-mix asphalt (HMA) mixtures. The objectives of this work were to (1) correlate fine aggregate expansions to the “parent” coarse aggregate expansions, (2) determine properties of dense-graded Pennsylvania ID-2 wearing coarse mixtures made with various sources of steel slag and crushed limestone fine aggregate, and (3) recommend appropriate specifications and test criteria for implementing the use of steel slag fine aggregate, if justifiable. Expansive characteristics of the steel slag aggregates were determined by Pennsylvania Test Method 130. HMA mixtures made with steel slag aggregates and limestone aggregate (control) were subjected to hot-water conditioning and Lottman freeze-and-thaw conditioning to determine potential problems, such as swell and moisture-induced damage. An excellent correlation existed between the average total expansion of the fine aggregate fraction and that of the “parent” coarse aggregate. No significant problems with swell and moisture-induced damage were noted in HMA mixtures containing steel slag fine aggregate and limestone coarse aggregate. Specifications and test criteria were recommended for the use of steel slag fine aggregate in HMA mixtures.